Magnetic field effect theory

If we are to use the radical pair theory to explain the effects of micellization on the cage reaction probability as well as the magnetic field effect, it is mandatory that we be able to observe CIDNP in these systems. In addition, since CIDNP is sensitive to events on the time scale of the radical pair lifetime, detailed analysis of the CIDNP can often lead to mechanistic insight to the dynamics of the radical pair. Below we describe one such result. 

Application of low, moderate, and strong magnetic fields (MFs) affects the escape of free radicals from a (viscous) solvent cage or from a microheterogeneous compartment such as a micelle. The theory of magnetic field effects (MFEs) is well described in a number of review articles. ... 

The microscopic approach has been particularly successful in the treatment of the Hall effect in electrolytes, summarized in an earlier overview [5]. As in the case of Hall conductivity, the magnitude of the magnetic field effect on diffusion is very small [6,7] but not negligible in a rigorous sense. The Llelmezs-Musbally formula [6] based on the theory of irreversible thermodynamics for bi-lonic systems ... 

MHD theory [9-14] has been applied extensively [e.g. 15-21] in conjunction with convective diffusion theory [22-26] to the analysis of external magnetic field effects in the hydrodynamic and concentration boundary layer existing at the electrode/electrolyte interface [2,5,27]. 

Magnetic fields are capable of generating, even at modest flux densities, i.e. less than one tesla. Important interactions with flow and structural phenomena. Since the magnetic force is often considerably less than force magnitudes associated with forced and natural convection in liquid electrolytes, classical MHD theory cannot be employed exclusively to explain all experimentally observed magnetic field effects. On the other hand, there exists at present no other cohesive theory for the treatment of electrlc/magnetic phenomena in liquids. The current lack of a comprehensive framework of analysis remains a serious challenge to all theoreticians, be they mathematicians, physicists or chemists. 

The Model II system was constructed to meet the more difficult requirements of sensitivity and time response, as previously mentioned. Three initial charging pressures, 286,5, 144, and 35.8 atm, were utilized, both in theory and experiment. These correspond to regime I, II, and III systems, respectively. The electrical nature of the pressure pickup required that the capillary tube be made exceptionally long to facilitate remote positioning against electric and magnetic field effects. 

However, the theory for the interaction of matter with the electromagnetic field has to be coherent. The finite field method, so gloriously successful in electric field effects, is in the stone age stage for magnetic field effects. The propagator methods look the most promising, these allow for easier calculation of NMR parameters than the sum-over-states methods. 

For convenience, the first case will be called the energy transfer and the second case will be called the quenching of electronic excitation. We first discuss the theory of collisional quenching (or transfer) in the absence of a magnetic field the theory will then be extended to include the magnetic-field effect. 

Fig. 1.3 Time line of ECL 1964-1965, first experiments 1965, theory 1966, transients 1969, magnetic field effects 1972, Ruffipy) 1977, oxalate 1981, aqueous 1982, Ruibpy) polymer and persulfate 1984, Ru(bpy) label 1987, tri-n-propylamine (TPA) 1989, bioassay 1993, ultramicroelectrodes 1998, laser action 2002, semiconductive nanocrystals (Reprinted with permission from Ref. [1]. Copyright 2008 American Chemical Society)...

The general theory of quasistatic magnetoelastic properties of the lanthanide compounds has been given in sect. 2 of this chapter. It involves a wide variety of possible types of low temperature behaviour and magnetic field effects on the lattice structure and elastic... 

The electric and magnetic fields appearing in Sections 2.3.1 and 2.3.2 have been described in terms of the SI system of units. The Gaussian system of cgs units has frequently been employed in the theory of liquid crystals when magnetic fields are discussed. Gaussian units are considered by many to be natural units for the calculation and measurement of magnetic field effects in liquid crystals. Since much of the literature contains results in both Gaussian units and SI units, it seems appropriate at this point to make some comments on the conversion from one system of units to the other. A comprehensive account of the points touched upon here may be found in Jackson [132] or Moskowitz [206]. Readers should also be famihar with derived SI units. 

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